In order to produce pipes, it is necessary to shape the cylindrical plastics melt flow produced by an extruder using a subsequent tool into an annular-gap-like melt flow. To this end, it is necessary for the melt flow originating from the extruder to be transferred in the tool by means of a centrally arranged mandrel into the corresponding annular flow. Such a device is proposed in DE 103 15 906.
Nowadays, short extrusion lines are often required. This can be achieved only when the cooling of the extruded profiles is optimised. At best, the melt is already cooled in the tool to such an extent that, although it is still deformable, the melt temperature is substantially lower than after leaving the extruder.
In this instance, DE 10 2007 050 291 proposes a division of the melt in the tool, the individual strands are cooled and subsequently combined again.
However, such a tool is difficult to operate for technical reasons relating to the method, since the flow behaviour of the cooled individual strands must be coordinated.